The casing ring is usually secured to the watch case by means of clamps and/or screws. However, such assembly methods have a certain number of drawbacks. Indeed, the thickness of the clamps and screw heads may prove inconvenient and result in excessive thickness of the parts. Further, the size of the screws requires a specific tool and a certain amount of experience for the assembly operation.
Thus, it has already been proposed to assembly a casing ring in a watch case without the necessity of using additional means such as screws or clamps.
EP Patent No 1312989 discloses such a device for assembling a casing ring to a watch case. More specifically, this document discloses a watch case including truncated housings machined in the inner wall of the watch case and a casing ring including at least two truncated chambers open on the rear and lateral faces of the ring. The truncated chambers are capable of receiving locking parts able to be moved in rotation from a free position, in which they are completely inside the chambers, to a locking position, in which they are partially housed in the chambers and partially inside corresponding housings in the case.
The assembly device described above has several drawbacks. First, it will be mentioned that the locking parts are removable, which involves a meticulous assembly of the casing ring once the locking parts are in place, since the casing ring must remain flat to avoid dislodging one or more of the locking parts. Next, it will be mentioned that the locking parts are of small size, which means they are difficult to handle during assembly of the watch. Finally, it will be observed that both the watch case and the casing ring require complex machining operations due to the shape of the locking parts.